The present invention is directed to bicycle components and, more particularly, to a bicycle derailleur which can be quickly installed to and removed from a bicycle frame.
Conventional bicycle rear derailleurs comprise a base member, a movable member supporting a chain guide, and a linkage mechanism coupling the base member to the movable member so that the movable member moves relative to the base member. The movable member includes a guide pulley for guiding the chain to one of a plurality of sprockets attached to the rear wheel. A through bore is usually formed in the base member, and a fixing bolt is fitted within the through bore for screwing the base member either directly to the bicycle frame or to a separate fixing member which, in turn, is directly attached to the bicycle frame. The derailleur is usually positioned below the rear wheel axle.
In order to operate properly, the radial position of guide pulley relative to the plurality of sprockets should be properly set. For derailleurs which have the base member rigidly fixed to the bicycle frame, the radial position of the guide pulley is set by adjusting the rotational position of the base member until the guide pulley has the desired position, and then the fixing bolt is tightened using a wrench. If the radial position of the guide pulley is to be readjusted, then the fixing bolt is loosened with the wrench, the rotational position of the base member is readjusted until the guide pulley has the desired new position, and then the fixing bolt is retightened with the wrench. The adjustment operation thus requires substantial effort and requires special tools. Furthermore, since the base member is usually positioned offset from the wheel axle, rotation of the base member to adjust the radial position of the guide pulley does not produce an intuitively predictable positioning of the guide pulley. Additionally, different frame manufacturers have different configurations for the attachment location of the derailleur. Not only does this further complicate the adjustment operation, but the derailleur designer cannot design a single derailleur that will work properly for all frame designs.
Another problem resulting from mounting the base member to the frame offset from the wheel axle is that the derailleur interferes with easy removal of the wheel. More specifically, the derailleur must be manually rotated so that the wheel can clear the derailleur when the wheel is removed from the frame. The derailleur again must be rotated when the wheel is to be reinstalled. The entire procedure often heavily soils the rider's hands, which can be very bothersome if the wheel must be removed to fix a flat.